Deepest ever ‘Blue hole’ discovered is 1,300ft deep and scientists still don’t know what’s at the bottom

The world's largest ever 'blue hole' has been discovered, but we don't know what's at the bottom because we haven't made it down there yet.

In Chetumal Bay, just off the coastline of Mexico and Belize, there is an incredibly deep blue hole.

First discovered in 2021, researchers initially thought it was 900ft deep, which would have made it the second deepest hole of its kind.

It seemed to come so close, and yet so far to matching the depth and majesty of the 990ft deep Sansha Yongle Blue Hole in the South China Sea.

However, new measurements of the Taam Ja' Blue Hole found that it was actually 1,380 feet deep which allow it to greatly surpass its rival and take the top spot.

Mexico's Taam Ja’ Blue Hole is the deepest in the world, but we don't fully know what's down there. (Joan A. Sánchez-Sánchez)

From rising to new heights to plumbing new depths, the next step for researchers would be to reach the bottom of this hole.

Writing in a study which was published on Monday (29 April) in Frontiers in Marine Science, the experts explained how they discovered that the Taam Ja' Blue Hole was even deeper than expected.

They wrote: "On December 6, 2023, a scuba diving expedition was conducted to identify the environmental conditions prevailing at the TJBH."

As part of their experiments they used something called a conductivity, temperature and depth (CTD) profiler, a gizmo that uses probes to transmit information about water through a cable.

What they found was that the blue hole they were exploring was deeper than they thought and deeper than any ever found before in the world, and we still haven't reached the bottom.

It's the deepest ever blue hole, that we know of at least. (Frontiers in Marine Science)

What they did manage to learn was a layer of water below the 1,312 mark resembled the Caribbean Sea, leading researchers to wonder if there was a series of tunnels in the hole which was connecting it to the sea.

We don't even know if there's even more depth to this hole than we now think, as the CTD profiler can go down to depths of 1,640 feet but stopped at 1,380.

Whether this means it could go no further or that the cable wasn't going down as far as it possibly could, we don't know.

As for what blue holes are, they're underwater caverns and sinkholes which tend to have different layers of water in them.

Remarkably deep, exploring them holds a certain level of fascination as it seems humans can't see a big hole without wondering what's at the bottom.

Sometimes expeditions into the holes find the bodies of divers who ran into trouble while exploring.